The construction industry often desires to employ excavations of various types, such as foundations, trenches, and the like. Where excavations are made in the earth, it is desirable to support the upright sidewalls of the excavation against collapse or to protect a sheltered work space in the event of collapse. Due to unstable soil conditions, improper sloping of an excavation and/or other unaccounted for occurrences, landslides and cave-ins ensue. These natural occurrences have been known to destroy equipment, postpone job completion and, most seriously, injure or kill the workers within the excavation. Consequently, trench excavation is recognized by the Occupational Safety and Health Administration (“OSHA”) as being an extremely hazardous construction operation and it has promulgated regulations directed to the manner in which excavations are created and to the structures used to support the excavations against sidewall collapse.
Current practice in the industry is to place trench boxes inside an excavation site. The trench boxes generally are open at the bottom so that excavation can continue while the boxes are in place and open at the top for easy access by men and machinery and easy removal of excavated materials. The primary structure of a trench box is comprised of opposing side panels that perform a shoring or shielding function by holding the sidewalls of the excavation in place, preventing the sidewalls from collapsing into the trench or hole in the ground created by excavating. Additionally, trench boxes usually have a plurality of bars or beams that transverse the lateral width of the trench box, attaching to opposing trench box panels and reinforcing or supporting the opposing panels, thus providing further protection from sidewall collapse. These support bars are also known as spreader bars as they assist in keeping the panels sufficiently spread apart from each other.
It is often desirable that the width between the opposing panels be changed and/or the angle of opposing planar panel surfaces of the trench box be increased or decreased (from parallel), which can be unsafe and time-consuming, especially when the trench box already is in place within the excavation. In particular, fine adjustments often are desired. More specifically, there is a need to be able to adjust the space and/or angle between the opposing panels of the trench box, particularly when the trench box is being driven into or pulled from the excavation.
Spreader bars currently in use are adjustable in length only in limited ways, such as by use of spreader bars or components thereof that have different fixed lengths, by manipulating angled components of predetermined lengths so as to create an outward extension of the support device, or by use of a hydraulic motor to extend the spreader bar when needed.
For example, U.S. Pat. No. 2,956,409 to Wicke (hereinafter the “'409 patent”) describes an adjustable bracing apparatus for shoring walls where the width of the device is adjusted either by having different, wider lengths of rigid brace or support members between the vertical side panels, or by extending connecting rods outwardly causing internal shafts to slide to accommodate a corresponding extension of said shafts.
Also, U.S. Pat. No. 3,362,168 to Dotlich (hereinafter the “'168 patent”) shows an apparatus for supporting the vertical walls of a trench that includes a hydraulic motor mechanism that maintains the side panels of the apparatus in shoring engagement with the vertical walls being adaptable to trench excavations of different lengths through use of pipe extensions of different lengths.
Notably, the '409 and '168 patents are limited in that neither can be used to push apart and pull together the opposing panels while in use as easily and precisely as the instant invention.